Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Graphic Smoking Images on Cigarette Packs Challenged by Judge

The U.S. government's power to force tobacco companies to put new graphic warning images on cigarette packages was questioned Wednesday by a federal judge.

Tobacco companies have filed a lawsuit to block the Food and Drug Administration requirement that would take effect in a year.

In Wednesday's two-hour hearing, U.S. District Judge Richard Leon grilled a justice department lawyer about whether the new graphic warning images simply relay facts of the health risks of smoking or cross the line into advocacy. That would be a crucial distinction in a case over free speech, the Associated Press reported.

If Leon decides the new images do amount to advocacy, it would improve the chances that the tobacco companies' would be able to stop the new regulation. The judge said he hopes to issue a ruling by the end of October.

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Gay Teen's Suicide Occurs Just Before Anti-Bullying Summit

The recent suicide of a gay Buffalo, N.Y. teen who was the victim of bullying coincides with a national summit on bullying prevention.

Jamey Rodemeyer, 14, killed himself on the weekend after posting an online farewell. The student at Williamsville North High School had been the target of cyberbullies for the past year, ABC News reported.

The second annual Federal Partners in Bullying Prevention Summit is being held today in Washington, D.C. and is sponsored by the U.S. Department of Education. Speakers at the conference include parents of another gay teen who killed himself after suffering relentless bullying.

Rodemeyer's suicide also marks a sad start to LGBT History Month in October.

"Jamey's suicide is a tragic reminder of the vulnerability of gay teens," Malcolm Lazin, founder and executive director of the Equality Forum, which focuses on LGBT civil rights and education, told ABC News.

"They are bullied and marginalized," he said. "While some may say that Jamey took his life, it is unrelenting homophobia that murdered him."

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Research Casts Doubt on 'Longevity Protein'

A new study challenges the theory that proteins called sirtuins can prolong life.

Previous research has suggested that elevated levels of sirtuins could extend life by up to 50 percent, but this new study found no such evidence, Agence France-Presse reported.

"We have re-examined the key experiments linking sirtuin with longevity in animals and none seem to stand up to close scrutiny," study leader David Gem, of the Institute of Healthy Aging at University College London, said in news release. "Sirtuins, far from being a key to longevity, appear to have nothing to do with extending life."

The study appears in the journal Nature.

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Dangerous Polio Strain Spreads to China

A "dangerous strain" of polio has spread from Pakistan to China, the World Health Organization says.

A WHO spokesman explained that the wild poliovirus type 1 is more dangerous than type 3 because it spreads more easily and is more likely to cause paralysis, the Associated Press reported.

In the past two months, seven cases of the WPV1 strain have been confirmed in China's Xinjiang province, which borders Pakistan.

The WHO says travelers to Pakistan need to be vaccinated against polio and that countries need to boost their surveillance for the WPV1 strain, the AP reported.

According to the U.S. Centers for Disease Control and Prevention, there is currently no danger of contracting the strain of polio in the United States, although travelers to foreign countries where it is endemic do need to be cautious. The CDC advises that travelers talk to their doctors about the risks before they depart.